With this little Calculator you can easily and fast find out all kgV's and ggT's of as many numbers you want. Just a little project and yea, have fun :)
Don't overdo it with the hight of the numbers because if there are too many numerals in a variable it will just say "infinity" what of course breaks the code ;-) If it needs more than like 5 seconds you probably broke the code or you, yea, should rally buy yourself a new PC :)